Usually in a display device, for the purpose of a good reproduction of an image represented by a video signal provided from outside as an input signal, gradation or the like indicated by the input signal is corrected for adjusting a relationship between a gradation value indicated by the input signal and a luminance value of an image actually displayed. Such correction is called “gamma correction”.
A liquid crystal display device displays an image represented by an input signal by controlling an applied voltage of liquid crystal according to the input signal and thereby changing light transmittance of the liquid crystal. In such a liquid crystal display device, the gamma correction is also carried out by correcting the gradation value or the like indicated by the input signal according to a relationship between the applied voltage and the transmittance of the liquid crystal (hereinafter, referred to as “VT characteristics”).
Meanwhile, the liquid crystal display device controls the transmittance by applying a voltage across a liquid crystal layer sandwiched between a pair of polarizer plates and thereby changing a phase difference (retardation) of the liquid crystal layer. Recently, a vertical alignmnent (VA) mode of the liquid crystal is used for an application to a television (TV) and a monitor, which is a normally black mode showing a black image without the applied voltage and provides a high quality black image and a high contrast. In this VA mode, the retardation of the liquid crystal has a wavelength dependence. Therefore, in a color liquid crystal display device which displays a color image using three kinds of pixels, R (red), G (green), and B (blue), the VT characteristics are slightly different among the three kinds of pixels.
Accordingly, there has been conventionally proposed a liquid crystal display device which carries out the gamma correction independently for each R, G, and B for obtaining a good color reproducibility in a displayed image (hereinafter, such a gamma correction carried out independently for each R, G, and B is referred to as “RGB independent gamma correction”, or simply “independent gamma correction”). For example, Japanese Unexamined Patent Application Publication No. 2002-258813 (patent reference 1) discloses a color liquid crystal display device which determines γ-curves of R, G, and B individually by generating gradation voltages independently for each R, G, and B (carries out the independent gamma correction). Also, Japanese Unexamined Patent Application Publication No. 2001-222264 (patent reference 2) discloses a liquid crystal display device including a storage means for storing gamma correction data for R, G, and B generated on the basis of each luminance characteristics of an R pixel, G pixel, and B pixel arranged in a matrix on a liquid crystal panel, and a gamma correction means for individually correcting an R signal, G signal, and B signal composing a video signal to be supplied to the R pixel, G pixel, and B pixel, respectively, on the basis of the gamma correction data for R, G, and B (carrying out the independent gamma correction).    Patent reference 1: Japanese Unexamined Patent Application Publication No. 2002-258813    Patent reference 2: Japanese Unexamined Patent Application Publication No. 2001-222264    Patent reference 3: Japanese Unexamined Patent Application Publication No. 2004-78157    Patent reference 4: Japanese Unexamined Patent Application Publication No. 2004-62146    Patent reference 5: Japanese Unexamined Patent Application Publication No. 2005-173573